"I can't tell you what it is, but I can tell you it's going to end his career," Clooney quipped. "I actually am working on something for [Brad] but I want to wait until, you know, for a while. Let it run for a couple of years."

Clooney's girlfriend Stacy Keibler chimed in to joke that she's the one person that doesn't fear the actor's elaborate jokes.

"We have a rule that he is not allowed to play pranks on me," Keibler said.